The present invention relates to a pneumatic tire, more particularly to a tread pattern including variable depth sipes capable of improving wear resistance of the tread without sacrificing tire performance on ice.
In order to improve running performance on snowy and icy roads, pneumatic tires for heavy duty vehicles such as truck and bus are usually provided with a block type tread pattern. Such a block type tread pattern often includes siped blocks in order to further improve running performance on ice (on-the-ice performance) for example as disclosed in Japanese Patent Application Publication No. 2009-190677.
In general, a siped block is reduced in the rigidity when compared with the non-siped block. Accordingly, its deformation and motion during running becomes larger. Therefore, a siped block is liable to wear easily.
In order to increase the wear resistance of a siped block, if the length and depth of the sipe are decreased, on-the-ice performance is naturally deteriorated.